Location Routing Numbers (LRN): What and Why?

The Telecommunications Act of 1996 represented a massive overhaul of U.S. telecommunications policy, and in a real sense reflected the redefinition of “telecommunications” that was being brought about due to converging elements of the industry.
Among many other things, the Act mandated that any telephone carrier could enter a local market. This meant that telephone carriers needed to provide the means by which customers could move their phone services from one provider to another while retaining their existing phone numbers.
A new system needed to be crafted to ascertain where a number resided in the virtual sense so that service providers could efficiently determine to which new carrier and specific telephone a call should be routed. This was ultimately called the Number Portability Administration Center (NPAC).
Origins of the LRN
In order to facilitate this process, the Location Routing Number (LRN) was devised. These are distinctive numerical designations that employ a 10-digit telephone number format to route phone calls to numbers that have been transferred from one carrier to another. Each switch in a discrete geographic area is tagged with the number, which then acts as a network address. On the new carrier’s end, the system is cued to perform a database query in order to obtain the LRN corresponding to the destination telephone number.
The 1996 ruling determined that every number transferred to an alternate carrier must be assigned an LRN. Before then, the determination of a given telephone number’s address lay with the Numbering Plan Area-Numbering Plan Exchange (NPA-NXX). It identified the service provider, carrier type (whether wireline or wireless), and the state and rate center where the phone number had originally been assigned.
Thumbnail: How It Works
The LRN negated the necessity for rate center, state, service provider, and carrier type identification; it only recognizes the switch that the number is associated with.
In practice, it works this way: When a local service provider receives a local call, the system looks at the number dialed to see if it contains a portable code. The dialed number is then tagged with a prefix code and 10-digit query, which is dipped into the routing database. The database returns the LRN associated with the number dialed. This all occurs at lightning speed from the customer’s perspective.
A number that has never been ported will not have an LRN, so it is routed based on its NPA-NXX. Once it has been ported it will have an LRN, and from that time forward it can be routed through recognition of the NPA-NXX of the LRN.
Jurisdictional Routing and Costs
Jurisdictional routing is call routing through the recognition of originating and destination telephone numbers and encompasses intrastate and interstate routes. Most wholesale Voice over Internet Protocol (VoIP) providers route termination calls in this manner. Carriers using this method can elect to dip for a ported number’s LRN; if they do not, they may pay a higher rate for that call.
While all of this remains invisible to the eyes of consumers, they would probably be surprised to learn that only a relatively small section of the Telecommunications Act of 1996 gave rise to the technological infrastructure which affords them such an invaluable convenience.